Car won't start? A guide to troubleshooting starting problems

A guide to troubleshooting starting problems

It’s happened to almost all drivers at some point: you hop in the car, turn the key or hit the ignition button, but nothing happens. For reasons unknown, your car won't start, and you're not going anywhere. What's more, you can hardly pop along to the nearest garage to get your vehicle repaired when you can't even get it off the driveway. It's certainly a frustrating experience.

So, what's to be done? With a little mechanical know-how, it is possible to fix the problem yourself and get your car back out on the road. But first, you need to diagnose the reason your car won't start.

In this guide to troubleshooting car starting problems, we'll share ten of the most common causes, along with some tips on how to identify and fix the issue:

1. The battery is flat

By far the most common cause of a car that won't start is a flat battery. The car battery stores the electrical energy needed to create a spark and ignite the engine, and if there's not enough power in the battery, the car won't start. The most obvious sign your battery has died is if you can hear a clicking sound when you turn the key in the ignition, but the engine does not turn over.

All sorts of things can put added strain on the battery, from a spell of very cold weather to leaving the car standing for a while. Or, you may have left one of your car's electrical consumers, like the lights, on overnight, which will gradually drain the battery. The battery might also simply be old, as they do need replacing every 3–4 years.

How to repair it: Testing the battery using a voltmeter will tell you whether or not you have a flat battery on your hands. If so, you'll need to jump-start it to get it going again. If jumping it still doesn't work, then you may need to replace the battery completely. You can read all about this in our guide to testing, jumping, and changing a car battery.

Sometimes, battery issues are caused by a bad alternator. This is a part that acts like a generator, providing the electrical energy needed to keep your engine and all of your vehicle’s electrical systems ticking. Some of this electrical power is stored the battery, which provides the burst of energy needed to create a spark and ignite the engine when you turn the key in the ignition. If the alternator is faulty, the battery may not charge properly, meaning the car won't be able to start. You can resolve this issue by testing and changing the alternator.

2. The battery terminals are dirty or corroded

Car battery terminals (where the cable meets the battery) are frequently exposed to acidic fumes from the battery acid, meaning that they often become corroded over time. Signs of corrosion include a light white or blue powdery build-up around the battery terminals and along the cable. If left untreated for long enough, the connection to the cables will be compromised, and the car may fail to start. So, if your car won’t start, you’ll want to check the battery terminals for signs of corrosion.

How to repair it: You can resolve this issue by cleaning the battery terminals using a specialist battery-cleaning product or bicarbonate of soda solution, which will work to neutralise any acidic corrosion. If the terminals have become severely corroded, you may need to change the battery completely.

3. The engine starter is faulty

The starter motor gets the engine going by transmitting power from the battery to the engine. When there’s a problem with this part, it means your engine isn’t getting the electrical power it needs to ignite.

If you hear a single, loud click when you turn the ignition, it’s a sign that there may be a fault with the engine starter or starter relay. You may also find that other electrical consumers in the vehicle, like the internal lights or dashboard, still work — it's just the engine that doesn't start.

How to fix it: A professional will be able to diagnose a faulty starter for you. If you have some mechanical expertise yourself, you can try testing the functionality of the starter using your car owner's manual and a voltmeter. If there's a problem, you'll need to get the starter repaired or replaced.

Jumping the battery might also help fix the issue, but this is generally only a temporary fix — you'll probably just encounter the same problem next time your attempt to start the car. But, it can help you to get your car going in order to take it to your nearest garage for repairs.

4. The steering lock is jammed

If your car won't start because you can’t turn the ignition key, the steering lock may be jammed. Most modern cars are fitted with a security function that automatically locks the wheel to prevent anyone from moving the car when the key isn’t in the ignition. Sometimes, this lock can be triggered accidentally by the driver if the steering wheel is moved slightly after the ignition was switched off.

How to fix it: If the key is stuck fast in the ignition and won’t move, try turning the steering wheel slightly from side to side and gently twisting the key at the same time. This should unlock the steering and ignition and get you going.

Sometimes, the wheel itself might get jammed and prevent you from moving the wheel, perhaps because you’re parked against a kerb. You can fix this by carefully releasing the handbrake, allowing the car to roll a little away from the kerb — keep your foot pressed down on the brake pedal to ensure you remain fully in control when doing this. This should free up the wheels, allowing you to turn the steering wheel a little as described above.

5. The power cables are loose or dodgy

The battery cables transmit electrical energy to the engine and other electric systems. Faulty, loose, or dirty battery cables can compromise the connection between the battery and the engine, meaning there’s not enough energy to start the car. If the cables are damaged, you may notice slow engine cranking or clicking sounds during cranking.

How to fix it: The best way to diagnose the problem is to visually inspect your cables for damage, fraying, or cracks. If you notice any problems at all, you’ll want to replace them as soon as possible — new cables aren't particularly expensive, but they can really help to extend the life of your battery, so it’s well worth doing. In cases where damage is extensive, both the cables and the clamps will need replacing.

6. Faulty or worn out distributor

The distributor, distributor cap, and rotor are essential parts of your car’s ignition system. They’re responsible for passing voltage from the ignition coils to the engine cylinders in order to create a spark at just the right time to ignite the fuel in the engine. If the distributor develops a fault, or if it isn’t secured tightly enough, the engine won’t be able to transmit the spark through the entire circuit to move the cylinders, meaning the car won’t start.

The distributor cap can be especially vulnerable to damp and moisture. So, if you have a problem starting after a spell of rain, it could be this causing the problem.

How to repair it: First, inspect the cap and rotor to work out whether they've developed a fault. The internal and external surfaces should be clean, with no corrosion or rust on the surface or firing points. The rotor in particular needs to be in pristine condition, as this is where the spark moves from one terminal to another. Check it carefully for any burn marks or blackened areas. You should also check that both parts are fitted securely.

If you notice any signs of wear and tear or build-up of carbon, you'll need to replace the distributor cap and rotor.

7. Ignition coil

The ignition coil is a key part of your car's ignition system. It works by converting the 12-volt charge from the battery into the much more powerful voltage needed to arc across the spark plug gap, creating a spark that ignites the fuel and air mix inside the engine and starts the car.

Some older cars only have one ignition coil, but most modern makes and models have a coil for every engine cylinder. As the ignition coil plays such an important role in the ignition system, a faulty or damaged coil can cause a number of engine problems, like misfiring, stalling, or even a complete failure to start at all.

How to fix it: First, you’ll want to establish whether or not this part is causing the problem by testing your ignition coil. Once an ignition coil has developed a fault, it can't be repaired, so you'll need to fully replace it. Should you need to do this, we would also recommend fitting new spark plugs at the same time, as this will help the new ignition coil last longer.

8. There's a problem with the spark plugs

Spark plugs are the parts of the ignition system that transmit an electrical charge from the ignition coil at exactly the right time to create a spark. This spark ignites the air and fuel mixture in the combustion chamber, firing up the engine and powering the vehicle.

Every car needs a clean set of spark plugs set at exactly the right distance in order to burn fuel efficiently. When the spark plugs become misaligned, damaged, or dirty, the spark won't fire at the right time, leading to starting problems.

How to fix it: You can test the spark plugs to find out if they're functioning as they should be. If they look a little dirty, you can also try cleaning them and re-adjusting the width to prolong their lifespan.

If cleaning them doesn’t solve the issue, or you suspect there's a more serious problem, you can try fitting new spark plugs. Replacing them every few years will ensure the best possible fuel efficiency for your vehicle, so it's well worth doing this if it's been a while since you last replaced them. You can find the recommended replacement intervals in your car owner's manual.

9. You've run out of fuel

It might sound obvious, but if you don’t have enough fuel in your tank, you won't be going anywhere! While it’s an easy enough mistake to make, you never want to allow your car to completely run out of fuel, as this will force the engine to start drawing in more air, which can cause serious damage.

If you suspect the fuel level may have dropped drastically since you last parked, it could be a sign that the fuel tank indicator is faulty or that you’ve sprung a leak somewhere. If this is the case, you may see smoke coming from your car exhaust, which could be a number of different colours depending on the exact problem. The problem could also be caused by a clogged fuel filter cutting off the fuel supply to the engine. So, you’ll want to get this checked out as soon as possible.

How to fix it: Fortunately, this one is easy to fix — all you need to do is find some more fuel. So, take a plastic emergency fuel container (it’s always best to have one of these stored in your boot) and head to the nearest petrol station. Remember that you should always ask an attendant for help when filling up a container, as it can be a bit messier and fiddlier than filling up your car's tank.

10. The fuel filter is clogged

Another common culprit behind a broken-down car is a clogged fuel filter. For your vehicle to run smoothly, the engine needs a perfectly balanced mix of clean fuel and air. The function of the fuel filter is to stop contaminants, dust, and debris from compromising the fuel supply and getting inside the engine, which can cause serious damage. When the filter becomes too clogged up, it can disrupt the supply of petrol or diesel to the engine, meaning there won't be enough fuel to ignite and start your car.

How to repair it: It’s not always easy to tell if a dirty fuel filter is causing the starting problem, as the symptoms will often be the same as an empty fuel tank. Filters generally need to be changed once every 15,000–20,000 miles, depending on the make and model, so if it’s been a while since you last changed the fuel filter, this could be what's causing the issue.

Replacement fuel filters are inexpensive, so it’s well worth trying this to help fix the problem. If you have some mechanical know-how, you could always try fixing the problem by changing the fuel filter at home.

Once you've worked out why your car won't start, you can work on getting the problem fixed. It's worth bearing in mind that, while this guide includes some of the most common reasons why a car won't start, there may be any number of other issues at play, and this isn't an exhaustive list. So, if you still can't work out what's causing the problem, be sure to consult a professional mechanic.

If you prefer to carry out work at home to help keep the cost of repairs down, remember you can find everything you need to get your car on the road again at GSF Car Parts. We have a huge array of car service parts and car batteries to suit all makes and models — just enter the details of your vehicle in our product finder to see exactly the right parts for your car. You can also find more handy guides in our auto knowledge hub.